1. Field of the Invention
The present invention relates to a lubricating structure for an internal combustion engine and more particularly, it relates to a lubricant passage structure formed in a crankshaft of the engine.
2. Description of the Related Art
Generally, lubricating oil in the internal combustion engine is sucked up from an oil pan through the intermediary of a strainer by an oil pump. Thereafter, the pressure of lubricating oil is controlled by a pressure governor and subsequently, the oil is fed to a main gallery. Formed to branch off from the main gallery are respective oil holes (or lubricant passages) through which the lubricating oil is supplied to respective lubricating sections, for example, a moving valve system, the crank shaft and so on.
As one of the oil hole structures provided in the crankshaft, there is known a general H-shaped lubricating structure where parallel oil holes (i.e. parallel lubricant passages) are respectively formed in both each crank journal and each crank pin so as to be perpendicular to a line connecting a center of the crank journal with a center of the crank pin in the axial view of the crankshaft. In this lubricating structure, an additional oil hole is formed so as to connect the oil hole of the crank journal with the oil hole of the crank pin at respective intermediate portions thereof (Japanese Unexamined Patent Publication No. 7-27126).